spring-boot-2.0.3源码篇 - filter的注册，值得一看

前言

　　开心一刻

　　　　过年女婿来岳父家走亲戚，当时小舅子主就问：姐夫，你什么时候能给我姐幸福，让我姐好好享受生活的美好。你们这辈子不准备买一套大点的房子吗？姐夫说：现在没钱啊！不过我有一个美丽可爱的女儿，等长大后找个有钱的老公嫁了，那时我就能和你姐一起住大房子了。岳父不乐意的说了一句：当初我也是这么认为的，可惜未能如愿。

　　路漫漫其修远兮，吾将上下而求索！

　　github：https://github.com/youzhibing

　　码云(gitee)：https://gitee.com/youzhibing

ServletContext

　　ServletContext介绍

　　　　定义了servlet与其servlet容器通信的一些列方法，例如，获取文件的MIME类型，分派请求或写入日志文件。

　　　　Servlet的运行模式是一个典型的“握手型的交互式”运行模式。所谓“握手型的交互式”就是两个模块为了交换数据通常都会准备一个交易场景，这个场景一直跟随这个交易过程直到这个交易完成为止。这个交易场景的初始化是根据这次交易对象指定的参数来定制的，这些制定参数通常就是一个配置类。所以对号入座，交易场景由ServletContext来描述，而定制的参数集合由ServletConfig来描述。而ServletRequest和ServletResponse就是要交互的具体对象，它们通常都作为运输工具来传递交互结果。ServletContext，即servlet上下文，用于存放web应用信息；每个Java虚拟机每个Web项目只有一个ServletContext，它是由Web服务器创建，代表当前web应用。

　　Servlet 3.0规范之前

　　　　我们采用2.5来看下源码

　　　　maven依赖

    javax.servlet
    servlet-api
    2.5
    provided

View Code

　　　　源码

/*
 * The contents of this file are subject to the terms
 * of the Common Development and Distribution License
 * (the "License").  You may not use this file except
 * in compliance with the License.
 *
 * You can obtain a copy of the license at
 * glassfish/bootstrap/legal/CDDLv1.0.txt or
 * https://glassfish.dev.java.net/public/CDDLv1.0.html.
 * See the License for the specific language governing
 * permissions and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL
 * HEADER in each file and include the License file at
 * glassfish/bootstrap/legal/CDDLv1.0.txt.  If applicable,
 * add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your
 * own identifying information: Portions Copyright [yyyy]
 * [name of copyright owner]
 *
 * Copyright 2005 Sun Microsystems, Inc. All rights reserved.
 *
 * Portions Copyright Apache Software Foundation.
 */

package javax.servlet;

import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Enumeration;
import java.util.Set;


/**
 * 
 * Defines a set of methods that a servlet uses to communicate with its
 * servlet container, for example, to get the MIME type of a file, dispatch
 * requests, or write to a log file.
 *
 * 
There is one context per "web application" per Java Virtual Machine.  (A
 * "web application" is a collection of servlets and content installed under a
 * specific subset of the server's URL namespace such as /catalog
 * and possibly installed via a .war file.) 
 *
 * 
In the case of a web
 * application marked "distributed" in its deployment descriptor, there will
 * be one context instance for each virtual machine.  In this situation, the 
 * context cannot be used as a location to share global information (because
 * the information won't be truly global).  Use an external resource like 
 * a database instead.
 *
 * 
The ServletContext object is contained within 
 * the {@link ServletConfig} object, which the Web server provides the
 * servlet when the servlet is initialized.
 *
 * @author     Various
 *
 * @see     Servlet#getServletConfig
 * @see     ServletConfig#getServletContext
 *
 */

public interface ServletContext {

    /**
     * Returns the context path of the web application.
     *
     * 
The context path is the portion of the request URI that is used
     * to select the context of the request. The context path always comes
     * first in a request URI. The path starts with a "/" character but does
     * not end with a "/" character. For servlets in the default (root)
     * context, this method returns "".
     *
     * 
It is possible that a servlet container may match a context by
     * more than one context path. In such cases the
     * {@link javax.servlet.http.HttpServletRequest#getContextPath()}
     * will return the actual context path used by the request and it may
     * differ from the path returned by this method.
     * The context path returned by this method should be considered as the
     * prime or preferred context path of the application.
     *
     * @return The context path of the web application, or "" for the
     * default (root) context
     *
     * @see javax.servlet.http.HttpServletRequest#getContextPath()
     *
     * @since Servlet 2.5
     */
    public String getContextPath();


    /**
     * Returns a ServletContext object that 
     * corresponds to a specified URL on the server.
     *
     * 
This method allows servlets to gain
     * access to the context for various parts of the server, and as
     * needed obtain {@link RequestDispatcher} objects from the context.
     * The given path must be begin with "/", is interpreted relative 
     * to the server's document root and is matched against the context roots of
     * other web applications hosted on this container.
     * 
     * 
In a security conscious environment, the servlet container may
     * return null for a given URL.
     *       
     * @param uripath     a String specifying the context path of
     *            another web application in the container.
     * @return        the ServletContext object that
     *            corresponds to the named URL, or null if either
            none exists or the container wishes to restrict 
     *             this access.
     *
     * @see         RequestDispatcher
     *
     */

    public ServletContext getContext(String uripath);
    
    

    /**
     * Returns the major version of the Java Servlet API that this
     * servlet container supports. All implementations that comply
     * with Version 2.5 must have this method
     * return the integer 2.
     *
     * @return         2
     *
     */
    
    public int getMajorVersion();
    
    

    /**
     * Returns the minor version of the Servlet API that this
     * servlet container supports. All implementations that comply
     * with Version 2.5 must have this method
     * return the integer 5.
     *
     * @return         5
     *
     */

    public int getMinorVersion();
    
    

    /**
     * Returns the MIME type of the specified file, or null if 
     * the MIME type is not known. The MIME type is determined
     * by the configuration of the servlet container, and may be specified
     * in a web application deployment descriptor. Common MIME
     * types are "text/html" and "image/gif".
     *
     *
     * @param   file    a String specifying the name
     *            of a file
     *
     * @return         a String specifying the file's MIME type
     *
     */

    public String getMimeType(String file);
    
    /**
    * Returns a directory-like listing of all the paths to resources within the web application whose longest sub-path
    * matches the supplied path argument. Paths indicating subdirectory paths end with a '/'. The returned paths are all 
    * relative to the root of the web application and have a leading '/'. For example, for a web application 
    * containing



    * /welcome.html

    * /catalog/index.html

    * /catalog/products.html

    * /catalog/offers/books.html

    * /catalog/offers/music.html

    * /customer/login.jsp

    * /WEB-INF/web.xml

    * /WEB-INF/classes/com.acme.OrderServlet.class,


    *
    * getResourcePaths("/") returns {"/welcome.html", "/catalog/", "/customer/", "/WEB-INF/"}

    * getResourcePaths("/catalog/") returns {"/catalog/index.html", "/catalog/products.html", "/catalog/offers/"}.

       


    *@param path        the partial path used to match the resources,
    *                which must start with a /
    *@return a Set containing the directory listing, or null if there are no resources in the web application whose path
    * begins with the supplied path.

    * @since Servlet 2.3
    */
    
    public Set getResourcePaths(String path);
    
    

    /**
     * Returns a URL to the resource that is mapped to a specified
     * path. The path must begin with a "/" and is interpreted
     * as relative to the current context root.
     *
     * 
This method allows the servlet container to make a resource 
     * available to servlets from any source. Resources 
     * can be located on a local or remote
     * file system, in a database, or in a .war file. 
     *
     * 
The servlet container must implement the URL handlers
     * and URLConnection objects that are necessary
     * to access the resource.
     *
     * 
This method returns null
     * if no resource is mapped to the pathname.
     *
     * 
Some containers may allow writing to the URL returned by
     * this method using the methods of the URL class.
     *
     * 
The resource content is returned directly, so be aware that 
     * requesting a .jsp page returns the JSP source code.
     * Use a RequestDispatcher instead to include results of 
     * an execution.
     *
     * 
This method has a different purpose than
     * java.lang.Class.getResource,
     * which looks up resources based on a class loader. This
     * method does not use class loaders.
     * 
     * @param path                 a String specifying
     *                        the path to the resource
     *
     * @return                     the resource located at the named path,
     *                         or null if there is no resource
     *                        at that path
     *
     * @exception MalformedURLException     if the pathname is not given in 
     *                         the correct form
     *
     */
    
    public URL getResource(String path) throws MalformedURLException;
    
    

    /**
     * Returns the resource located at the named path as
     * an InputStream object.
     *
     * 
The data in the InputStream can be 
     * of any type or length. The path must be specified according
     * to the rules given in getResource.
     * This method returns null if no resource exists at
     * the specified path. 
     * 
     * 
Meta-information such as content length and content type
     * that is available via getResource
     * method is lost when using this method.
     *
     * 
The servlet container must implement the URL handlers
     * and URLConnection objects necessary to access
     * the resource.
     *
     * 
This method is different from 
     * java.lang.Class.getResourceAsStream,
     * which uses a class loader. This method allows servlet containers 
     * to make a resource available
     * to a servlet from any location, without using a class loader.
     * 
     *
     * @param path     a String specifying the path
     *            to the resource
     *
     * @return         the InputStream returned to the 
     *            servlet, or null if no resource
     *            exists at the specified path 
     *
     *
     */

    public InputStream getResourceAsStream(String path);
    



    /**
     * 
     * Returns a {@link RequestDispatcher} object that acts
     * as a wrapper for the resource located at the given path.
     * A RequestDispatcher object can be used to forward 
     * a request to the resource or to include the resource in a response.
     * The resource can be dynamic or static.
     *
     * 
The pathname must begin with a "/" and is interpreted as relative
     * to the current context root.  Use getContext to obtain
     * a RequestDispatcher for resources in foreign contexts.
     * This method returns null if the ServletContext
     * cannot return a RequestDispatcher.
     *
     * @param path     a String specifying the pathname
     *            to the resource
     *
     * @return         a RequestDispatcher object
     *            that acts as a wrapper for the resource
     *            at the specified path, or null if 
     *            the ServletContext cannot return
     *            a RequestDispatcher
     *
     * @see         RequestDispatcher
     * @see         ServletContext#getContext
     *
     */

    public RequestDispatcher getRequestDispatcher(String path);



    /**
     * Returns a {@link RequestDispatcher} object that acts
     * as a wrapper for the named servlet.
     *
     * 
Servlets (and JSP pages also) may be given names via server 
     * administration or via a web application deployment descriptor.
     * A servlet instance can determine its name using 
     * {@link ServletConfig#getServletName}.
     *
     * 
This method returns null if the 
     * ServletContext
     * cannot return a RequestDispatcher for any reason.
     *
     * @param name     a String specifying the name
     *            of a servlet to wrap
     *
     * @return         a RequestDispatcher object
     *            that acts as a wrapper for the named servlet,
     *            or null if the ServletContext
     *            cannot return a RequestDispatcher
     *
     * @see         RequestDispatcher
     * @see         ServletContext#getContext
     * @see         ServletConfig#getServletName
     *
     */

    public RequestDispatcher getNamedDispatcher(String name);
    
    
    
    
    /**
     *
     * @deprecated    As of Java Servlet API 2.1, with no direct replacement.
     *
     * 
This method was originally defined to retrieve a servlet
     * from a ServletContext. In this version, this method 
     * always returns null and remains only to preserve 
     * binary compatibility. This method will be permanently removed 
     * in a future version of the Java Servlet API.
     *
     * 
In lieu of this method, servlets can share information using the 
     * ServletContext class and can perform shared business logic
     * by invoking methods on common non-servlet classes.
     *
     */

    public Servlet getServlet(String name) throws ServletException;
    
  
  
  
    

    /**
     *
     * @deprecated    As of Java Servlet API 2.0, with no replacement.
     *
     * 
This method was originally defined to return an Enumeration
     * of all the servlets known to this servlet context. In this
     * version, this method always returns an empty enumeration and
     * remains only to preserve binary compatibility. This method
     * will be permanently removed in a future version of the Java
     * Servlet API.
     *
     */
    
    public Enumeration getServlets();
    
    
    
    
    

    /**
     * @deprecated    As of Java Servlet API 2.1, with no replacement.
     *
     * 
This method was originally defined to return an 
     * Enumeration
     * of all the servlet names known to this context. In this version,
     * this method always returns an empty Enumeration and 
     * remains only to preserve binary compatibility. This method will 
     * be permanently removed in a future version of the Java Servlet API.
     *
     */
 
    public Enumeration getServletNames();
    
  
  
    
    
    /**
     *
     * Writes the specified message to a servlet log file, usually
     * an event log. The name and type of the servlet log file is 
     * specific to the servlet container.
     *
     *
     * @param msg     a String specifying the 
     *            message to be written to the log file
     *
     */
     
    public void log(String msg);
    
    
    
    

    /**
     * @deprecated    As of Java Servlet API 2.1, use
     *             {@link #log(String message, Throwable throwable)} 
     *            instead.
     *
     * 
This method was originally defined to write an 
     * exception's stack trace and an explanatory error message
     * to the servlet log file.
     *
     */

    public void log(Exception exception, String msg);
    
    
    
    

    /**
     * Writes an explanatory message and a stack trace
     * for a given Throwable exception
     * to the servlet log file. The name and type of the servlet log 
     * file is specific to the servlet container, usually an event log.
     *
     *
     * @param message         a String that 
     *                describes the error or exception
     *
     * @param throwable     the Throwable error 
     *                or exception
     *
     */
    
    public void log(String message, Throwable throwable);
    
    
    
    
    
    /**
     * Returns a String containing the real path 
     * for a given virtual path. For example, the path "/index.html"
     * returns the absolute file path on the server's filesystem would be
     * served by a request for "http://host/contextPath/index.html",
     * where contextPath is the context path of this ServletContext..
     *
     * 
The real path returned will be in a form
     * appropriate to the computer and operating system on
     * which the servlet container is running, including the
     * proper path separators. This method returns null
     * if the servlet container cannot translate the virtual path
     * to a real path for any reason (such as when the content is
     * being made available from a .war archive).
     *
     *
     * @param path     a String specifying a virtual path
     *
     *
     * @return         a String specifying the real path,
     *                  or null if the translation cannot be performed
     *            
     *
     */

    public String getRealPath(String path);
    
    


    /**
     * Returns the name and version of the servlet container on which
     * the servlet is running. 
     *
     * 
The form of the returned string is 
     * servername/versionnumber.
     * For example, the JavaServer Web Development Kit may return the string
     * JavaServer Web Dev Kit/1.0.
     *
     * 
The servlet container may return other optional information 
     * after the primary string in parentheses, for example,
     * JavaServer Web Dev Kit/1.0 (JDK 1.1.6; Windows NT 4.0 x86).
     *
     *
     * @return         a String containing at least the 
     *            servlet container name and version number
     *
     */

    public String getServerInfo();
    
    


    /**
     * Returns a String containing the value of the named
     * context-wide initialization parameter, or null if the 
     * parameter does not exist.
     *
     * 
This method can make available configuration information useful
     * to an entire "web application".  For example, it can provide a 
     * webmaster's email address or the name of a system that holds 
     * critical data.
     *
     * @param    name    a String containing the name of the
     *                  parameter whose value is requested
     * 
     * @return         a String containing at least the 
     *            servlet container name and version number
     *
     * @see ServletConfig#getInitParameter
     */

    public String getInitParameter(String name);
    
    


    /**
     * Returns the names of the context's initialization parameters as an
     * Enumeration of String objects, or an
     * empty Enumeration if the context has no initialization
     * parameters.
     *
     * @return         an Enumeration of String 
     *                  objects containing the names of the context's
     *                  initialization parameters
     *
     * @see ServletConfig#getInitParameter
     */

    public Enumeration getInitParameterNames();
    
    

    /**
     * Returns the servlet container attribute with the given name, 
     * or null if there is no attribute by that name.
     * An attribute allows a servlet container to give the
     * servlet additional information not
     * already provided by this interface. See your
     * server documentation for information about its attributes.
     * A list of supported attributes can be retrieved using
     * getAttributeNames.
     *
     * 
The attribute is returned as a java.lang.Object
     * or some subclass.
     * Attribute names should follow the same convention as package
     * names. The Java Servlet API specification reserves names
     * matching java.*, javax.*,
     * and sun.*.
     *
     *
     * @param name     a String specifying the name 
     *            of the attribute
     *
     * @return         an Object containing the value 
     *            of the attribute, or null
     *            if no attribute exists matching the given
     *            name
     *
     * @see         ServletContext#getAttributeNames
     *
     */
  
    public Object getAttribute(String name);
    
    
    

    /**
     * Returns an Enumeration containing the 
     * attribute names available
     * within this servlet context. Use the
     * {@link #getAttribute} method with an attribute name
     * to get the value of an attribute.
     *
     * @return         an Enumeration of attribute 
     *            names
     *
     * @see        #getAttribute
     *
     */

    public Enumeration getAttributeNames();
    
    
    
    
    /**
     *
     * Binds an object to a given attribute name in this servlet context. If
     * the name specified is already used for an attribute, this
     * method will replace the attribute with the new to the new attribute.
     * 
If listeners are configured on the ServletContext the  
     * container notifies them accordingly.
     * 

     * If a null value is passed, the effect is the same as calling 
     * removeAttribute().
     * 
     * 
Attribute names should follow the same convention as package
     * names. The Java Servlet API specification reserves names
     * matching java.*, javax.*, and
     * sun.*.
     *
     *
     * @param name     a String specifying the name 
     *            of the attribute
     *
     * @param object     an Object representing the
     *            attribute to be bound
     *
     *
     *
     */
    
    public void setAttribute(String name, Object object);
    
    



    /**
     * Removes the attribute with the given name from 
     * the servlet context. After removal, subsequent calls to
     * {@link #getAttribute} to retrieve the attribute's value
     * will return null.

     * 
If listeners are configured on the ServletContext the 
     * container notifies them accordingly.

     *
     *
     * @param name    a String specifying the name 
     *             of the attribute to be removed
     *
     */

    public void removeAttribute(String name);
    
    /**
     * Returns the name of this web application corresponding to this ServletContext as specified in the deployment
     * descriptor for this web application by the display-name element.
     *
     *
     * @return        The name of the web application or null if no name has been declared in the deployment descriptor.
     * @since Servlet 2.3
     */
    
    public String getServletContextName();
}

View Code

　　　　定义了 一些列的方法，具体就不看了，有兴趣的可以详细看下

　　Servlet 3.0+ 规范

　　　　我们采用4.0.1来看下源码

　　　　maven依赖

    javax.servlet
    javax.servlet-api
    4.0.1
    provided

View Code

　　　　源码

/*
 * Copyright (c) 1997-2018 Oracle and/or its affiliates. All rights reserved.
 * Copyright 2004 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package javax.servlet;

import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Enumeration;
import java.util.EnumSet;
import java.util.EventListener;
import java.util.Map;
import java.util.Set;
import javax.servlet.descriptor.JspConfigDescriptor;

/**
 * Defines a set of methods that a servlet uses to communicate with its
 * servlet container, for example, to get the MIME type of a file,
 * dispatch requests, or write to a log file.
 *
 * 
There is one context per "web application" per Java Virtual Machine.  (A
 * "web application" is a collection of servlets and content installed under a
 * specific subset of the server's URL namespace such as /catalog
 * and possibly installed via a .war file.)
 *
 * 
In the case of a web
 * application marked "distributed" in its deployment descriptor, there will
 * be one context instance for each virtual machine.  In this situation, the
 * context cannot be used as a location to share global information (because
 * the information won't be truly global).  Use an external resource like
 * a database instead.
 *
 * 
The ServletContext object is contained within
 * the {@link ServletConfig} object, which the Web server provides the
 * servlet when the servlet is initialized.
 *
 * @author     Various
 *
 * @see     Servlet#getServletConfig
 * @see     ServletConfig#getServletContext
 */

public interface ServletContext {

    /**
     * The name of the ServletContext attribute which stores
     * the private temporary directory (of type java.io.File)
     * provided by the servlet container for the ServletContext
     */
    public static final String TEMPDIR = "javax.servlet.context.tempdir";


    /**
     * The name of the ServletContext attribute whose value
     * (of type java.util.List<java.lang.String>) contains
     * the list of names of JAR files in WEB-INF/lib ordered by
     * their web fragment names (with possible exclusions if
     * <absolute-ordering> without any
     * <others/> is being used), or null if no
     * absolute or relative ordering has been specified
     */
    public static final String ORDERED_LIBS =
        "javax.servlet.context.orderedLibs";


    /**
     * Returns the context path of the web application.
     *
     * 
The context path is the portion of the request URI that is used
     * to select the context of the request. The context path always comes
     * first in a request URI. If this context is the "root" context
     * rooted at the base of the Web server's URL name space, this path
     * will be an empty string. Otherwise, if the context is not rooted at
     * the root of the server's name space, the path starts with a /
     * character but does not end with a / character.
     *
     * 
It is possible that a servlet container may match a context by
     * more than one context path. In such cases the
     * {@link javax.servlet.http.HttpServletRequest#getContextPath()}
     * will return the actual context path used by the request and it may
     * differ from the path returned by this method.
     * The context path returned by this method should be considered as the
     * prime or preferred context path of the application.
     *
     * @return The context path of the web application, or "" for the
     * root context
     *
     * @see javax.servlet.http.HttpServletRequest#getContextPath()
     *
     * @since Servlet 2.5
     */
    public String getContextPath();


    /**
     * Returns a ServletContext object that
     * corresponds to a specified URL on the server.
     *
     * 
This method allows servlets to gain
     * access to the context for various parts of the server, and as
     * needed obtain {@link RequestDispatcher} objects from the context.
     * The given path must be begin with /, is interpreted relative
     * to the server's document root and is matched against the context
     * roots of other web applications hosted on this container.
     *
     * 
In a security conscious environment, the servlet container may
     * return null for a given URL.
     *
     * @param uripath     a String specifying the context path of
     *            another web application in the container.
     * @return        the ServletContext object that
     *            corresponds to the named URL, or null if either
            none exists or the container wishes to restrict
     *             this access.
     *
     * @see         RequestDispatcher
     */
    public ServletContext getContext(String uripath);


    /**
     * Returns the major version of the Servlet API that this
     * servlet container supports. All implementations that comply
     * with Version 4.0 must have this method return the integer 4.
     *
     * @return 4
     */
    public int getMajorVersion();


    /**
     * Returns the minor version of the Servlet API that this
     * servlet container supports. All implementations that comply
     * with Version 4.0 must have this method return the integer 0.
     *
     * @return 0
     */
    public int getMinorVersion();


    /**
     * Gets the major version of the Servlet specification that the
     * application represented by this ServletContext is based on.
     *
     * 
The value returned may be different from {@link #getMajorVersion},
     * which returns the major version of the Servlet specification
     * supported by the Servlet container.
     *
     * @return the major version of the Servlet specification that the
     * application represented by this ServletContext is based on
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @since Servlet 3.0
     */
    public int getEffectiveMajorVersion();


    /**
     * Gets the minor version of the Servlet specification that the
     * application represented by this ServletContext is based on.
     *
     * 
The value returned may be different from {@link #getMinorVersion},
     * which returns the minor version of the Servlet specification
     * supported by the Servlet container.
     *
     * @return the minor version of the Servlet specification that the
     * application represented by this ServletContext is based on
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @since Servlet 3.0
     */
    public int getEffectiveMinorVersion();


    /**
     * Returns the MIME type of the specified file, or null if
     * the MIME type is not known. The MIME type is determined
     * by the configuration of the servlet container, and may be specified
     * in a web application deployment descriptor. Common MIME
     * types include text/html and image/gif.
     *
     * @param file a String specifying the name of a file
     *
     * @return a String specifying the file's MIME type
     */
    public String getMimeType(String file);


    /**
     * Returns a directory-like listing of all the paths to resources
     * within the web application whose longest sub-path matches the
     * supplied path argument.
     *
     * 
Paths indicating subdirectory paths end with a /.
     *
     * 
The returned paths are all relative to the root of the web
     * application, or relative to the /META-INF/resources
     * directory of a JAR file inside the web application's
     * /WEB-INF/lib directory, and have a leading /.
     *
     * 
The returned set is not backed by the {@code ServletContext} object,
     * so changes in the returned set are not reflected in the
     * {@code ServletContext} object, and vice-versa.
     *
     * 
For example, for a web application containing:
     *
     * 
{@code
     *   /welcome.html
     *   /catalog/index.html
     *   /catalog/products.html
     *   /catalog/offers/books.html
     *   /catalog/offers/music.html
     *   /customer/login.jsp
     *   /WEB-INF/web.xml
     *   /WEB-INF/classes/com.acme.OrderServlet.class
     *   /WEB-INF/lib/catalog.jar!/META-INF/resources/catalog/moreOffers/books.html
     * }
     *
     * getResourcePaths("/") would return
     * {"/welcome.html", "/catalog/", "/customer/", "/WEB-INF/"},
     * and getResourcePaths("/catalog/") would return
     * {"/catalog/index.html", "/catalog/products.html",
     * "/catalog/offers/", "/catalog/moreOffers/"}.
     *
     * @param path the partial path used to match the resources,
     * which must start with a /
     * @return a Set containing the directory listing, or null if there
     * are no resources in the web application whose path
     * begins with the supplied path.
     *
     * @since Servlet 2.3
     */
    public Set getResourcePaths(String path);


    /**
     * Returns a URL to the resource that is mapped to the given path.
     *
     * 
The path must begin with a / and is interpreted
     * as relative to the current context root,
     * or relative to the /META-INF/resources directory
     * of a JAR file inside the web application's /WEB-INF/lib
     * directory.
     * This method will first search the document root of the
     * web application for the requested resource, before searching
     * any of the JAR files inside /WEB-INF/lib.
     * The order in which the JAR files inside /WEB-INF/lib
     * are searched is undefined.
     *
     * 
This method allows the servlet container to make a resource
     * available to servlets from any source. Resources
     * can be located on a local or remote
     * file system, in a database, or in a .war file.
     *
     * 
The servlet container must implement the URL handlers
     * and URLConnection objects that are necessary
     * to access the resource.
     *
     * 
This method returns null
     * if no resource is mapped to the pathname.
     *
     * 
Some containers may allow writing to the URL returned by
     * this method using the methods of the URL class.
     *
     * 
The resource content is returned directly, so be aware that
     * requesting a .jsp page returns the JSP source code.
     * Use a RequestDispatcher instead to include results of
     * an execution.
     *
     * 
This method has a different purpose than
     * java.lang.Class.getResource,
     * which looks up resources based on a class loader. This
     * method does not use class loaders.
     *
     * @param path a String specifying
     * the path to the resource
     *
     * @return the resource located at the named path,
     * or null if there is no resource at that path
     *
     * @exception MalformedURLException if the pathname is not given in
     * the correct form
     */
    public URL getResource(String path) throws MalformedURLException;


    /**
     * Returns the resource located at the named path as
     * an InputStream object.
     *
     * 
The data in the InputStream can be
     * of any type or length. The path must be specified according
     * to the rules given in getResource.
     * This method returns null if no resource exists at
     * the specified path.
     *
     * 
Meta-information such as content length and content type
     * that is available via getResource
     * method is lost when using this method.
     *
     * 
The servlet container must implement the URL handlers
     * and URLConnection objects necessary to access
     * the resource.
     *
     * 
This method is different from
     * java.lang.Class.getResourceAsStream,
     * which uses a class loader. This method allows servlet containers
     * to make a resource available
     * to a servlet from any location, without using a class loader.
     *
     *
     * @param path     a String specifying the path
     *            to the resource
     *
     * @return         the InputStream returned to the
     *            servlet, or null if no resource
     *            exists at the specified path
     */
    public InputStream getResourceAsStream(String path);


    /**
     *
     * Returns a {@link RequestDispatcher} object that acts
     * as a wrapper for the resource located at the given path.
     * A RequestDispatcher object can be used to forward
     * a request to the resource or to include the resource in a response.
     * The resource can be dynamic or static.
     *
     * 
The pathname must begin with a / and is interpreted as
     * relative to the current context root.  Use getContext
     * to obtain a RequestDispatcher for resources in foreign
     * contexts.
     *
     * 
This method returns null if the
     * ServletContext cannot return a
     * RequestDispatcher.
     *
     * @param path     a String specifying the pathname
     *            to the resource
     *
     * @return         a RequestDispatcher object
     *            that acts as a wrapper for the resource
     *            at the specified path, or null if
     *            the ServletContext cannot return
     *            a RequestDispatcher
     *
     * @see         RequestDispatcher
     * @see         ServletContext#getContext
     */
    public RequestDispatcher getRequestDispatcher(String path);


    /**
     * Returns a {@link RequestDispatcher} object that acts
     * as a wrapper for the named servlet.
     *
     * 
Servlets (and JSP pages also) may be given names via server
     * administration or via a web application deployment descriptor.
     * A servlet instance can determine its name using
     * {@link ServletConfig#getServletName}.
     *
     * 
This method returns null if the
     * ServletContext
     * cannot return a RequestDispatcher for any reason.
     *
     * @param name     a String specifying the name
     *            of a servlet to wrap
     *
     * @return         a RequestDispatcher object
     *            that acts as a wrapper for the named servlet,
     *            or null if the ServletContext
     *            cannot return a RequestDispatcher
     *
     * @see         RequestDispatcher
     * @see         ServletContext#getContext
     * @see         ServletConfig#getServletName
     */
    public RequestDispatcher getNamedDispatcher(String name);


    /**
     * @deprecated    As of Java Servlet API 2.1, with no direct replacement.
     *
     * 
This method was originally defined to retrieve a servlet
     * from a ServletContext. In this version, this method
     * always returns null and remains only to preserve
     * binary compatibility. This method will be permanently removed
     * in a future version of the Java Servlet API.
     *
     * 
In lieu of this method, servlets can share information using the
     * ServletContext class and can perform shared business logic
     * by invoking methods on common non-servlet classes.
     *
     * @param name the servlet name
     * @return the {@code javax.servlet.Servlet Servlet} with the given name
     * @throws ServletException if an exception has occurred that interfaces
     *                          with servlet's normal operation
     */
    @Deprecated
    public Servlet getServlet(String name) throws ServletException;


    /**
     * @deprecated    As of Java Servlet API 2.0, with no replacement.
     *
     * 
This method was originally defined to return an
     * Enumeration of all the servlets known to this servlet
     * context.
     * In this version, this method always returns an empty enumeration and
     * remains only to preserve binary compatibility. This method
     * will be permanently removed in a future version of the Java
     * Servlet API.
     *
     * @return an Enumeration of {@code javax.servlet.Servlet Servlet}
     */
    @Deprecated
    public Enumeration getServlets();


    /**
     * @deprecated    As of Java Servlet API 2.1, with no replacement.
     *
     * 
This method was originally defined to return an
     * Enumeration
     * of all the servlet names known to this context. In this version,
     * this method always returns an empty Enumeration and
     * remains only to preserve binary compatibility. This method will
     * be permanently removed in a future version of the Java Servlet API.
     *
     * @return an Enumeration of {@code javax.servlet.Servlet Servlet} names
     */
    @Deprecated
    public Enumeration getServletNames();


    /**
     *
     * Writes the specified message to a servlet log file, usually
     * an event log. The name and type of the servlet log file is
     * specific to the servlet container.
     *
     * @param msg     a String specifying the
     *            message to be written to the log file
     */
    public void log(String msg);


    /**
     * @deprecated    As of Java Servlet API 2.1, use
     *             {@link #log(String message, Throwable throwable)}
     *            instead.
     *
     * 
This method was originally defined to write an
     * exception's stack trace and an explanatory error message
     * to the servlet log file.
     *
     * @param exception the Exception error
     * @param msg a String that describes the exception
     */
    @Deprecated
    public void log(Exception exception, String msg);


    /**
     * Writes an explanatory message and a stack trace
     * for a given Throwable exception
     * to the servlet log file. The name and type of the servlet log
     * file is specific to the servlet container, usually an event log.
     *
     * @param message         a String that
     *                describes the error or exception
     *
     * @param throwable     the Throwable error
     *                or exception
     */
    public void log(String message, Throwable throwable);


    /**
     * Gets the real path corresponding to the given
     * virtual path.
     *
     * 
For example, if path is equal to /index.html,
     * this method will return the absolute file path on the server's
     * filesystem to which a request of the form
     * http://<host>:<port>/<contextPath>/index.html
     * would be mapped, where <contextPath> corresponds to the
     * context path of this ServletContext.
     *
     * 
The real path returned will be in a form
     * appropriate to the computer and operating system on
     * which the servlet container is running, including the
     * proper path separators.
     *
     * 
Resources inside the /META-INF/resources
     * directories of JAR files bundled in the application's
     * /WEB-INF/lib directory must be considered only if the
     * container has unpacked them from their containing JAR file, in
     * which case the path to the unpacked location must be returned.
     *
     * 
This method returns null if the servlet container
     * is unable to translate the given virtual path to a
     * real path.
     *
     * @param path the virtual path to be translated to a
     * real path
     *
     * @return the real path, or null if the
     * translation cannot be performed
     */
    public String getRealPath(String path);


    /**
     * Returns the name and version of the servlet container on which
     * the servlet is running.
     *
     * 
The form of the returned string is
     * servername/versionnumber.
     * For example, the JavaServer Web Development Kit may return the string
     * JavaServer Web Dev Kit/1.0.
     *
     * 
The servlet container may return other optional information
     * after the primary string in parentheses, for example,
     * JavaServer Web Dev Kit/1.0 (JDK 1.1.6; Windows NT 4.0 x86).
     *
     *
     * @return         a String containing at least the
     *            servlet container name and version number
     */
    public String getServerInfo();


    /**
     * Returns a String containing the value of the named
     * context-wide initialization parameter, or null if
     * the parameter does not exist.
     *
     * 
This method can make available configuration information useful
     * to an entire web application.  For example, it can provide a
     * webmaster's email address or the name of a system that holds
     * critical data.
     *
     * @param    name    a String containing the name of the
     *                  parameter whose value is requested
     *
     * @return a String containing the value of the
     * context's initialization parameter, or null if the
     * context's initialization parameter does not exist.
     *
     * @throws NullPointerException if the argument {@code name} is
     * {@code null}
     *
     * @see ServletConfig#getInitParameter
     */
    public String getInitParameter(String name);


    /**
     * Returns the names of the context's initialization parameters as an
     * Enumeration of String objects, or an
     * empty Enumeration if the context has no initialization
     * parameters.
     *
     * @return         an Enumeration of String
     *                  objects containing the names of the context's
     *                  initialization parameters
     *
     * @see ServletConfig#getInitParameter
     */
    public Enumeration getInitParameterNames();


    /**
     * Sets the context initialization parameter with the given name and
     * value on this ServletContext.
     *
     * @param name the name of the context initialization parameter to set
     * @param value the value of the context initialization parameter to set
     *
     * @return true if the context initialization parameter with the given
     * name and value was set successfully on this ServletContext, and false
     * if it was not set because this ServletContext already contains a
     * context initialization parameter with a matching name
     *
     * @throws IllegalStateException if this ServletContext has already
     * been initialized
     *
     * @throws NullPointerException if the name parameter is {@code null}
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @since Servlet 3.0
     */
    public boolean setInitParameter(String name, String value);


    /**
     * Returns the servlet container attribute with the given name, or
     * null if there is no attribute by that name.
     *
     * 
An attribute allows a servlet container to give the
     * servlet additional information not
     * already provided by this interface. See your
     * server documentation for information about its attributes.
     * A list of supported attributes can be retrieved using
     * getAttributeNames.
     *
     * 
The attribute is returned as a java.lang.Object
     * or some subclass.
     *
     * 
Attribute names should follow the same convention as package
     * names. The Java Servlet API specification reserves names
     * matching java.*, javax.*,
     * and sun.*.
     *
     * @param name     a String specifying the name
     *            of the attribute
     *
     * @return an Object containing the value of the
     *            attribute, or null if no attribute
     *            exists matching the given name.
     *
     * @see         ServletContext#getAttributeNames
     *
     * @throws NullPointerException if the argument {@code name} is
     * {@code null}
     *
     */
    public Object getAttribute(String name);


    /**
     * Returns an Enumeration containing the
     * attribute names available within this ServletContext.
     *
     * 
Use the {@link #getAttribute} method with an attribute name
     * to get the value of an attribute.
     *
     * @return         an Enumeration of attribute
     *            names
     *
     * @see        #getAttribute
     */
    public Enumeration getAttributeNames();


    /**
     * Binds an object to a given attribute name in this ServletContext. If
     * the name specified is already used for an attribute, this
     * method will replace the attribute with the new to the new attribute.
     * 
If listeners are configured on the ServletContext the
     * container notifies them accordingly.
     * 

     * If a null value is passed, the effect is the same as calling
     * removeAttribute().
     *
     * 
Attribute names should follow the same convention as package
     * names. The Java Servlet API specification reserves names
     * matching java.*, javax.*, and
     * sun.*.
     *
     * @param name     a String specifying the name
     *            of the attribute
     *
     * @param object     an Object representing the
     *            attribute to be bound
     *
     * @throws NullPointerException if the name parameter is {@code null}
     *
     */
    public void setAttribute(String name, Object object);


    /**
     * Removes the attribute with the given name from
     * this ServletContext. After removal, subsequent calls to
     * {@link #getAttribute} to retrieve the attribute's value
     * will return null.
     *
     * 
If listeners are configured on the ServletContext the
     * container notifies them accordingly.
     *
     * @param name    a String specifying the name
     *             of the attribute to be removed
     */
    public void removeAttribute(String name);


    /**
     * Returns the name of this web application corresponding to this
     * ServletContext as specified in the deployment descriptor for this
     * web application by the display-name element.
     *
     * @return The name of the web application or null if no name has been
     * declared in the deployment descriptor.
     *
     * @since Servlet 2.3
     */
    public String getServletContextName();


    /**
     * Adds the servlet with the given name and class name to this servlet
     * context.
     *
     * 
The registered servlet may be further configured via the returned
     * {@link ServletRegistration} object.
     *
     * 
The specified className will be loaded using the
     * classloader associated with the application represented by this
     * ServletContext.
     *
     * 
If this ServletContext already contains a preliminary
     * ServletRegistration for a servlet with the given servletName,
     * it will be completed (by assigning the given className to it)
     * and returned.
     *
     * 
This method introspects the class with the given className
     * for the {@link javax.servlet.annotation.ServletSecurity},
     * {@link javax.servlet.annotation.MultipartConfig},
     * javax.annotation.security.RunAs, and
     * javax.annotation.security.DeclareRoles annotations.
     * In addition, this method supports resource injection if the
     * class with the given className represents a Managed Bean.
     * See the Java EE platform and JSR 299 specifications for additional
     * details about Managed Beans and resource injection.
     *
     * @param servletName the name of the servlet
     * @param className the fully qualified class name of the servlet
     *
     * @return a ServletRegistration object that may be used to further
     * configure the registered servlet, or null if this
     * ServletContext already contains a complete ServletRegistration for
     * a servlet with the given servletName
     *
     * @throws IllegalStateException if this ServletContext has already
     * been initialized
     *
     * @throws IllegalArgumentException if servletName is null
     * or an empty String
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @since Servlet 3.0
     */
    public ServletRegistration.Dynamic addServlet(
        String servletName, String className);


    /**
     * Registers the given servlet instance with this ServletContext
     * under the given servletName.
     *
     * 
The registered servlet may be further configured via the returned
     * {@link ServletRegistration} object.
     *
     * 
If this ServletContext already contains a preliminary
     * ServletRegistration for a servlet with the given servletName,
     * it will be completed (by assigning the class name of the given servlet
     * instance to it) and returned.
     *
     * @param servletName the name of the servlet
     * @param servlet the servlet instance to register
     *
     * @return a ServletRegistration object that may be used to further
     * configure the given servlet, or null if this
     * ServletContext already contains a complete ServletRegistration for a
     * servlet with the given servletName or if the same servlet
     * instance has already been registered with this or another
     * ServletContext in the same container
     *
     * @throws IllegalStateException if this ServletContext has already
     * been initialized
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @throws IllegalArgumentException if the given servlet instance
     * implements {@link SingleThreadModel}, or servletName is null
     * or an empty String
     *
     * @since Servlet 3.0
     */
    public ServletRegistration.Dynamic addServlet(
        String servletName, Servlet servlet);


    /**
     * Adds the servlet with the given name and class type to this servlet
     * context.
     *
     * 
The registered servlet may be further configured via the returned
     * {@link ServletRegistration} object.
     *
     * 
If this ServletContext already contains a preliminary
     * ServletRegistration for a servlet with the given servletName,
     * it will be completed (by assigning the name of the given
     * servletClass to it) and returned.
     *
     * 
This method introspects the given servletClass for
     * the {@link javax.servlet.annotation.ServletSecurity},
     * {@link javax.servlet.annotation.MultipartConfig},
     * javax.annotation.security.RunAs, and
     * javax.annotation.security.DeclareRoles annotations.
     * In addition, this method supports resource injection if the
     * given servletClass represents a Managed Bean.
     * See the Java EE platform and JSR 299 specifications for additional
     * details about Managed Beans and resource injection.
     *
     * @param servletName the name of the servlet
     * @param servletClass the class object from which the servlet will be
     * instantiated
     *
     * @return a ServletRegistration object that may be used to further
     * configure the registered servlet, or null if this
     * ServletContext already contains a complete ServletRegistration for
     * the given servletName
     *
     * @throws IllegalStateException if this ServletContext has already
     * been initialized
     *
     * @throws IllegalArgumentException if servletName is null
     * or an empty String
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @since Servlet 3.0
     */
    public ServletRegistration.Dynamic addServlet(String servletName,
        Class extends Servlet> servletClass);


    /**
     * Adds the servlet with the given jsp file to this servlet context.
     *
     * 
The registered servlet may be further configured via the returned
     * {@link ServletRegistration} object.
     *
     * 
If this ServletContext already contains a preliminary
     * ServletRegistration for a servlet with the given servletName,
     * it will be completed (by assigning the given jspFile to it)
     * and returned.
     *
     * @param servletName the name of the servlet
     * @param jspFile the full path to a JSP file within the web application
     *                beginning with a `/'.
     *
     * @return a ServletRegistration object that may be used to further
     * configure the registered servlet, or null if this
     * ServletContext already contains a complete ServletRegistration for
     * a servlet with the given servletName
     *
     * @throws IllegalStateException if this ServletContext has already
     * been initialized
     *
     * @throws IllegalArgumentException if servletName is null
     * or an empty String
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @since Servlet 4.0
     */
    public ServletRegistration.Dynamic addJspFile(
        String servletName, String jspFile);


    /**
     * Instantiates the given Servlet class.
     *
     * 
The returned Servlet instance may be further customized before it
     * is registered with this ServletContext via a call to
     * {@link #addServlet(String,Servlet)}.
     *
     * 
The given Servlet class must define a zero argument constructor,
     * which is used to instantiate it.
     *
     * 
This method introspects the given clazz for
     * the following annotations:
     * {@link javax.servlet.annotation.ServletSecurity},
     * {@link javax.servlet.annotation.MultipartConfig},
     * javax.annotation.security.RunAs, and
     * javax.annotation.security.DeclareRoles.
     * In addition, this method supports resource injection if the
     * given clazz represents a Managed Bean.
     * See the Java EE platform and JSR 299 specifications for additional
     * details about Managed Beans and resource injection.
     *
     * @param  the class of the Servlet to create
     * @param clazz the Servlet class to instantiate
     *
     * @return the new Servlet instance
     *
     * @throws ServletException if the given clazz fails to be
     * instantiated
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @since Servlet 3.0
     */
    public extends Servlet> T createServlet(Class clazz)
        throws ServletException;


    /**
     * Gets the ServletRegistration corresponding to the servlet with the
     * given servletName.
     *
     * @return the (complete or preliminary) ServletRegistration for the
     * servlet with the given servletName, or null if no
     * ServletRegistration exists under that name
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @param servletName the name of a servlet
     * @since Servlet 3.0
     */
    public ServletRegistration getServletRegistration(String servletName);


    /**
     * Gets a (possibly empty) Map of the ServletRegistration
     * objects (keyed by servlet name) corresponding to all servlets
     * registered with this ServletContext.
     *
     * 
The returned Map includes the ServletRegistration objects
     * corresponding to all declared and annotated servlets, as well as the
     * ServletRegistration objects corresponding to all servlets that have
     * been added via one of the addServlet and addJspFile
     * methods.
     *
     * 
If permitted, any changes to the returned Map must not affect this
     * ServletContext.
     *
     * @return Map of the (complete and preliminary) ServletRegistration
     * objects corresponding to all servlets currently registered with this
     * ServletContext
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @since Servlet 3.0
     */
    public Mapextends ServletRegistration> getServletRegistrations();


    /**
     * Adds the filter with the given name and class name to this servlet
     * context.
     *
     * 
The registered filter may be further configured via the returned
     * {@link FilterRegistration} object.
     *
     * 
The specified className will be loaded using the
     * classloader associated with the application represented by this
     * ServletContext.
     *
     * 
If this ServletContext already contains a preliminary
     * FilterRegistration for a filter with the given filterName,
     * it will be completed (by assigning the given className to it)
     * and returned.
     *
     * 
This method supports resource injection if the class with the
     * given className represents a Managed Bean.
     * See the Java EE platform and JSR 299 specifications for additional
     * details about Managed Beans and resource injection.
     *
     * @param filterName the name of the filter
     * @param className the fully qualified class name of the filter
     *
     * @return a FilterRegistration object that may be used to further
     * configure the registered filter, or null if this
     * ServletContext already contains a complete FilterRegistration for
     * a filter with the given filterName
     *
     * @throws IllegalStateException if this ServletContext has already
     * been initialized
     *
     * @throws IllegalArgumentException if filterName is null or
     * an empty String
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @since Servlet 3.0
     */
    public FilterRegistration.Dynamic addFilter(
        String filterName, String className);


    /**
     * Registers the given filter instance with this ServletContext
     * under the given filterName.
     *
     * 
The registered filter may be further configured via the returned
     * {@link FilterRegistration} object.
     *
     * 
If this ServletContext already contains a preliminary
     * FilterRegistration for a filter with the given filterName,
     * it will be completed (by assigning the class name of the given filter
     * instance to it) and returned.
     *
     * @param filterName the name of the filter
     * @param filter the filter instance to register
     *
     * @return a FilterRegistration object that may be used to further
     * configure the given filter, or null if this
     * ServletContext already contains a complete FilterRegistration for a
     * filter with the given filterName or if the same filter
     * instance has already been registered with this or another
     * ServletContext in the same container
     *
     * @throws IllegalStateException if this ServletContext has already
     * been initialized
     *
     * @throws IllegalArgumentException if filterName is null or
     * an empty String
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @since Servlet 3.0
     */
    public FilterRegistration.Dynamic addFilter(
        String filterName, Filter filter);


    /**
     * Adds the filter with the given name and class type to this servlet
     * context.
     *
     * 
The registered filter may be further configured via the returned
     * {@link FilterRegistration} object.
     *
     * 
If this ServletContext already contains a preliminary
     * FilterRegistration for a filter with the given filterName,
     * it will be completed (by assigning the name of the given
     * filterClass to it) and returned.
     *
     * 
This method supports resource injection if the given
     * filterClass represents a Managed Bean.
     * See the Java EE platform and JSR 299 specifications for additional
     * details about Managed Beans and resource injection.
     *
     * @param filterName the name of the filter
     * @param filterClass the class object from which the filter will be
     * instantiated
     *
     * @return a FilterRegistration object that may be used to further
     * configure the registered filter, or null if this
     * ServletContext already contains a complete FilterRegistration for a
     * filter with the given filterName
     *
     * @throws IllegalStateException if this ServletContext has already
     * been initialized
     *
     * @throws IllegalArgumentException if filterName is null or
     * an empty String
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @since Servlet 3.0
     */
    public FilterRegistration.Dynamic addFilter(String filterName,
        Class extends Filter> filterClass);


    /**
     * Instantiates the given Filter class.
     *
     * 
The returned Filter instance may be further customized before it
     * is registered with this ServletContext via a call to
     * {@link #addFilter(String,Filter)}.
     *
     * 
The given Filter class must define a zero argument constructor,
     * which is used to instantiate it.
     *
     * 
This method supports resource injection if the given
     * clazz represents a Managed Bean.
     * See the Java EE platform and JSR 299 specifications for additional
     * details about Managed Beans and resource injection.
     *
     * @param  the class of the Filter to create
     * @param clazz the Filter class to instantiate
     *
     * @return the new Filter instance
     *
     * @throws ServletException if the given clazz fails to be
     * instantiated
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @since Servlet 3.0
     */
    public extends Filter> T createFilter(Class clazz)
        throws ServletException;


    /**
     * Gets the FilterRegistration corresponding to the filter with the
     * given filterName.
     *
     * @param filterName the name of a filter
     * @return the (complete or preliminary) FilterRegistration for the
     * filter with the given filterName, or null if no
     * FilterRegistration exists under that name
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @since Servlet 3.0
     */
    public FilterRegistration getFilterRegistration(String filterName);


    /**
     * Gets a (possibly empty) Map of the FilterRegistration
     * objects (keyed by filter name) corresponding to all filters
     * registered with this ServletContext.
     *
     * 
The returned Map includes the FilterRegistration objects
     * corresponding to all declared and annotated filters, as well as the
     * FilterRegistration objects corresponding to all filters that have
     * been added via one of the addFilter methods.
     *
     * 
Any changes to the returned Map must not affect this
     * ServletContext.
     *
     * @return Map of the (complete and preliminary) FilterRegistration
     * objects corresponding to all filters currently registered with this
     * ServletContext
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @since Servlet 3.0
     */
    public Mapextends FilterRegistration> getFilterRegistrations();


    /**
     * Gets the {@link SessionCookieConfig} object through which various
     * properties of the session tracking cookies created on behalf of this
     * ServletContext may be configured.
     *
     * 
Repeated invocations of this method will return the same
     * SessionCookieConfig instance.
     *
     * @return the SessionCookieConfig object through which
     * various properties of the session tracking cookies created on
     * behalf of this ServletContext may be configured
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @since Servlet 3.0
     */
    public SessionCookieConfig getSessionCookieConfig();


    /**
     * Sets the session tracking modes that are to become effective for this
     * ServletContext.
     *
     * 
The given sessionTrackingModes replaces any
     * session tracking modes set by a previous invocation of this
     * method on this ServletContext.
     *
     * @param sessionTrackingModes the set of session tracking modes to
     * become effective for this ServletContext
     *
     * @throws IllegalStateException if this ServletContext has already
     * been initialized
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @throws IllegalArgumentException if sessionTrackingModes
     * specifies a combination of SessionTrackingMode.SSL with a
     * session tracking mode other than SessionTrackingMode.SSL,
     * or if sessionTrackingModes specifies a session tracking mode
     * that is not supported by the servlet container
     *
     * @since Servlet 3.0
     */
    public void setSessionTrackingModes(Set sessionTrackingModes);


    /**
     * Gets the session tracking modes that are supported by default for this
     * ServletContext.
     *
     * 
The returned set is not backed by the {@code ServletContext} object,
     * so changes in the returned set are not reflected in the
     * {@code ServletContext} object, and vice-versa.
     *
     * @return set of the session tracking modes supported by default for
     * this ServletContext
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @since Servlet 3.0
     */
    public Set getDefaultSessionTrackingModes();


    /**
     * Gets the session tracking modes that are in effect for this
     * ServletContext.
     *
     * 
The session tracking modes in effect are those provided to
     * {@link #setSessionTrackingModes setSessionTrackingModes}.
     *
     * 
The returned set is not backed by the {@code ServletContext} object,
     * so changes in the returned set are not reflected in the
     * {@code ServletContext} object, and vice-versa.
     *
     * @return set of the session tracking modes in effect for this
     * ServletContext
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @since Servlet 3.0
     */
    public Set getEffectiveSessionTrackingModes();


    /**
     * Adds the listener with the given class name to this ServletContext.
     *
     * 
The class with the given name will be loaded using the
     * classloader associated with the application represented by this
     * ServletContext, and must implement one or more of the following
     * interfaces:
     * 

     * 
{@link ServletContextAttributeListener}
     * 
{@link ServletRequestListener}
     * 
{@link ServletRequestAttributeListener}
     * 
{@link javax.servlet.http.HttpSessionAttributeListener}
     * 
{@link javax.servlet.http.HttpSessionIdListener}
     * 
{@link javax.servlet.http.HttpSessionListener}
     * 
     *
     * 
If this ServletContext was passed to
     * {@link ServletContainerInitializer#onStartup}, then the class with
     * the given name may also implement {@link ServletContextListener},
     * in addition to the interfaces listed above.
     *
     * 
As part of this method call, the container must load the class
     * with the specified class name to ensure that it implements one of
     * the required interfaces.
     *
     * 
If the class with the given name implements a listener interface
     * whose invocation order corresponds to the declaration order (i.e.,
     * if it implements {@link ServletRequestListener},
     * {@link ServletContextListener}, or
     * {@link javax.servlet.http.HttpSessionListener}),
     * then the new listener will be added to the end of the ordered list of
     * listeners of that interface.
     *
     * 
This method supports resource injection if the class with the
     * given className represents a Managed Bean.
     * See the Java EE platform and JSR 299 specifications for additional
     * details about Managed Beans and resource injection.
     *
     * @param className the fully qualified class name of the listener
     *
     * @throws IllegalArgumentException if the class with the given name
     * does not implement any of the above interfaces, or if it implements
     * {@link ServletContextListener} and this ServletContext was not
     * passed to {@link ServletContainerInitializer#onStartup}
     *
     * @throws IllegalStateException if this ServletContext has already
     * been initialized
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @since Servlet 3.0
     */
    public void addListener(String className);


    /**
     * Adds the given listener to this ServletContext.
     *
     * 
The given listener must be an instance of one or more of the
     * following interfaces:
     * 

     * 
{@link ServletContextAttributeListener}
     * 
{@link ServletRequestListener}
     * 
{@link ServletRequestAttributeListener}
     * 
{@link javax.servlet.http.HttpSessionAttributeListener}
     * 
{@link javax.servlet.http.HttpSessionIdListener}
     * 
{@link javax.servlet.http.HttpSessionListener}
     * 
     *
     * 
If this ServletContext was passed to
     * {@link ServletContainerInitializer#onStartup}, then the given
     * listener may also be an instance of {@link ServletContextListener},
     * in addition to the interfaces listed above.
     *
     * 
If the given listener is an instance of a listener interface whose
     * invocation order corresponds to the declaration order (i.e., if it
     * is an instance of {@link ServletRequestListener},
     * {@link ServletContextListener}, or
     * {@link javax.servlet.http.HttpSessionListener}),
     * then the listener will be added to the end of the ordered list of
     * listeners of that interface.
     *
     * @param  the class of the EventListener to add
     * @param t the listener to be added
     *
     * @throws IllegalArgumentException if the given listener is not
     * an instance of any of the above interfaces, or if it is an instance
     * of {@link ServletContextListener} and this ServletContext was not
     * passed to {@link ServletContainerInitializer#onStartup}
     *
     * @throws IllegalStateException if this ServletContext has already
     * been initialized
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @since Servlet 3.0
     */
    public extends EventListener> void addListener(T t);


    /**
     * Adds a listener of the given class type to this ServletContext.
     *
     * 
The given listenerClass must implement one or more of the
     * following interfaces:
     * 

     * 
{@link ServletContextAttributeListener}
     * 
{@link ServletRequestListener}
     * 
{@link ServletRequestAttributeListener}
     * 
{@link javax.servlet.http.HttpSessionAttributeListener}
     * 
{@link javax.servlet.http.HttpSessionIdListener}
     * 
{@link javax.servlet.http.HttpSessionListener}
     * 
     *
     * 
If this ServletContext was passed to
     * {@link ServletContainerInitializer#onStartup}, then the given
     * listenerClass may also implement
     * {@link ServletContextListener}, in addition to the interfaces listed
     * above.
     *
     * 
If the given listenerClass implements a listener
     * interface whose invocation order corresponds to the declaration order
     * (i.e., if it implements {@link ServletRequestListener},
     * {@link ServletContextListener}, or
     * {@link javax.servlet.http.HttpSessionListener}),
     * then the new listener will be added to the end of the ordered list
     * of listeners of that interface.
     *
     * 
This method supports resource injection if the given
     * listenerClass represents a Managed Bean.
     * See the Java EE platform and JSR 299 specifications for additional
     * details about Managed Beans and resource injection.
     *
     * @param listenerClass the listener class to be instantiated
     *
     * @throws IllegalArgumentException if the given listenerClass
     * does not implement any of the above interfaces, or if it implements
     * {@link ServletContextListener} and this ServletContext was not passed
     * to {@link ServletContainerInitializer#onStartup}
     *
     * @throws IllegalStateException if this ServletContext has already
     * been initialized
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @since Servlet 3.0
     */
    public void addListener(Class extends EventListener> listenerClass);


    /**
     * Instantiates the given EventListener class.
     *
     * 
The specified EventListener class must implement at least one of
     * the {@link ServletContextListener},
     * {@link ServletContextAttributeListener},
     * {@link ServletRequestListener},
     * {@link ServletRequestAttributeListener},
     * {@link javax.servlet.http.HttpSessionAttributeListener},
     * {@link javax.servlet.http.HttpSessionIdListener}, or
     * {@link javax.servlet.http.HttpSessionListener}
     * interfaces.
     *
     * 
The returned EventListener instance may be further customized
     * before it is registered with this ServletContext via a call to
     * {@link #addListener(EventListener)}.
     *
     * 
The given EventListener class must define a zero argument
     * constructor, which is used to instantiate it.
     *
     * 
This method supports resource injection if the given
     * clazz represents a Managed Bean.
     * See the Java EE platform and JSR 299 specifications for additional
     * details about Managed Beans and resource injection.
     *
     * @param  the class of the EventListener to create
     * @param clazz the EventListener class to instantiate
     *
     * @return the new EventListener instance
     *
     * @throws ServletException if the given clazz fails to be
     * instantiated
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @throws IllegalArgumentException if the specified EventListener class
     * does not implement any of the
     * {@link ServletContextListener},
     * {@link ServletContextAttributeListener},
     * {@link ServletRequestListener},
     * {@link ServletRequestAttributeListener},
     * {@link javax.servlet.http.HttpSessionAttributeListener},
     * {@link javax.servlet.http.HttpSessionIdListener}, or
     * {@link javax.servlet.http.HttpSessionListener}
     * interfaces.
     *
     * @since Servlet 3.0
     */
    public extends EventListener> T createListener(Class clazz)
        throws ServletException;


    /**
     * Gets the <jsp-config> related configuration
     * that was aggregated from the web.xml and
     * web-fragment.xml descriptor files of the web application
     * represented by this ServletContext.
     *
     * @return the <jsp-config> related configuration
     * that was aggregated from the web.xml and
     * web-fragment.xml descriptor files of the web application
     * represented by this ServletContext, or null if no such configuration
     * exists
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @see javax.servlet.descriptor.JspConfigDescriptor
     *
     * @since Servlet 3.0
     */
    public JspConfigDescriptor getJspConfigDescriptor();


    /**
     * Gets the class loader of the web application represented by this
     * ServletContext.
     *
     * 
If a security manager exists, and the caller's class loader
     * is not the same as, or an ancestor of the requested class loader,
     * then the security manager's checkPermission method is
     * called with a RuntimePermission("getClassLoader")
     * permission to check whether access to the requested class loader
     * should be granted.
     *
     * @return the class loader of the web application represented by this
     * ServletContext
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @throws SecurityException if a security manager denies access to
     * the requested class loader
     *
     * @since Servlet 3.0
     */
    public ClassLoader getClassLoader();


    /**
     * Declares role names that are tested using isUserInRole.
     *
     * 
Roles that are implicitly declared as a result of their use within
     * the {@link ServletRegistration.Dynamic#setServletSecurity
     * setServletSecurity} or {@link ServletRegistration.Dynamic#setRunAsRole
     * setRunAsRole} methods of the {@link ServletRegistration} interface need
     * not be declared.
     *
     * @param roleNames the role names being declared
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @throws IllegalArgumentException if any of the argument roleNames is
     * null or the empty string
     *
     * @throws IllegalStateException if the ServletContext has already
     * been initialized
     *
     * @since Servlet 3.0
     */
    public void declareRoles(String... roleNames);


    /**
     * Returns the configuration name of the logical host on which the
     * ServletContext is deployed.
     *
     * Servlet containers may support multiple logical hosts. This method must
     * return the same name for all the servlet contexts deployed on a logical
     * host, and the name returned by this method must be distinct, stable per
     * logical host, and suitable for use in associating server configuration
     * information with the logical host. The returned value is NOT expected
     * or required to be equivalent to a network address or hostname of the
     * logical host.
     *
     * @return a String containing the configuration name of the
     * logical host on which the servlet context is deployed.
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @since Servlet 3.1
     */
    public String getVirtualServerName();


    /**
     * Gets the session timeout in minutes that are supported by default for
     * this ServletContext.
     *
     * @return the session timeout in minutes that are supported by default for
     * this ServletContext
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @since Servlet 4.0
     */
    public int getSessionTimeout();


    /**
     * Sets the session timeout in minutes for this ServletContext.
     *
     * @param sessionTimeout session timeout in minutes
     *
     * @throws IllegalStateException if this ServletContext has already
     * been initialized
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @since Servlet 4.0
     */
    public void setSessionTimeout(int sessionTimeout);


    /**
     * Gets the request character encoding that are supported by default for
     * this ServletContext. This method returns null if no request
     * encoding character encoding has been specified in deployment descriptor
     * or container specific configuration (for all web applications in the
     * container).
     *
     * @return the request character encoding that are supported by default for
     * this ServletContext
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @since Servlet 4.0
     */
    public String getRequestCharacterEncoding();


    /**
     * Sets the request character encoding for this ServletContext.
     *
     * @param encoding request character encoding
     *
     * @throws IllegalStateException if this ServletContext has already
     * been initialized
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @since Servlet 4.0
     */
    public void setRequestCharacterEncoding(String encoding);


    /**
     * Gets the response character encoding that are supported by default for
     * this ServletContext. This method returns null if no response
     * encoding character encoding has been specified in deployment descriptor
     * or container specific configuration (for all web applications in the
     * container).
     *
     * @return the request character encoding that are supported by default for
     * this ServletContext
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @since Servlet 4.0
     */
    public String getResponseCharacterEncoding();


    /**
     * Sets the response character encoding for this ServletContext.
     *
     * @param encoding response character encoding
     *
     * @throws IllegalStateException if this ServletContext has already
     * been initialized
     *
     * @throws UnsupportedOperationException if this ServletContext was
     * passed to the {@link ServletContextListener#contextInitialized} method
     * of a {@link ServletContextListener} that was neither declared in
     * web.xml or web-fragment.xml, nor annotated
     * with {@link javax.servlet.annotation.WebListener}
     *
     * @since Servlet 4.0
     */
    public void setResponseCharacterEncoding(String encoding);
}

View Code

　　　　从3.0新增的方法，方法描述上都有标明@since Servlet 3.0，大家可以去细看下3.0具体新增了哪些方法。新增的add系列方法如下

　　　　也就是说可以通过ServletContext向servlet容器添加Filter、Listener和Servlet了。

　　补充

　　　　3.0之前和3.0之后，maven依赖的artifactId是不同的，大家需要注意一下；

　　　　servlet 3.0是一个大的版本变动，相比之前增加了比较多的特性，本文就涉及到其中一个特性：支持无web.xml配置（新的注解支持）

　　　　servlet 3.0及之后，Filter、Servlet和Listener支持注解配置（3.0之前都是配置在web.xml中）

Filter注册

　　springboot实现

　　　　实现Filter接口实现我们自己的Filter，这个与web.xml时期一样

package com.lee.register.filter;

import javax.servlet.*;
import java.io.IOException;

public class MyFilter implements Filter {

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("myfilter init...");
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        System.out.println("过滤处理");
        chain.doFilter(request, response);
    }

    @Override
    public void destroy() {
        System.out.println("myfilter destroy...");
    }
}

View Code

　　　　利用FilterRegistrationBean将我们自定义的Filter注册到容器

package com.lee.register.config;

import com.lee.register.filter.MyFilter;
import com.lee.register.listener.MyListener;
import com.lee.register.servlet.MyServlet;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.boot.web.servlet.ServletListenerRegistrationBean;
import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import java.util.Arrays;

@Configuration
public class MyConfig {

    @Bean
    public ServletListenerRegistrationBean myListener() {
        ServletListenerRegistrationBean registrationBean = new ServletListenerRegistrationBean(new MyListener());
        return registrationBean;
    }

    @Bean
    public FilterRegistrationBean myFilter() {
        FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean(new MyFilter());
        filterRegistrationBean.setUrlPatterns(Arrays.asList("/hello","/myServlet"));
        return filterRegistrationBean;
    }

    @Bean
    public ServletRegistrationBean myServlet() {
        ServletRegistrationBean registrationBean = new ServletRegistrationBean(new MyServlet());
        registrationBean.setUrlMappings(Arrays.asList("/myServlet"));
        registrationBean.setLoadOnStartup(1);
        return registrationBean;
    }
}

View Code

　　　　工程详情请点：spring-boot-filter；FilterRegistrationBean的作用与在web.xml中配置Filter类似，只是底层用了servlet3.0的新特性

　　源码分析

　　　　我们知道servlet3.0+，可以通过ServeltContext来注册Filter（当然还包括Servlet、Listener）到Servlet容器；至于注册到Servlet容器后，容器容器如何处理Filter就不是本文的范畴了。我们姑且这样认为：通过ServletContext注册Filter到容器，那么Filter就能起到过滤作用了。那么问题来了，springboot是如何将Filter注册到容器的？

　　　　FilterRegistrationBean的源码

/*
 * Copyright 2012-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.boot.web.servlet;

import javax.servlet.Filter;
import javax.servlet.ServletContext;

import org.springframework.util.Assert;

/**
 * A {@link ServletContextInitializer} to register {@link Filter}s in a Servlet 3.0+
 * container. Similar to the {@link ServletContext#addFilter(String, Filter) registration}
 * features provided by {@link ServletContext} but with a Spring Bean friendly design.
 * 

 * The {@link #setFilter(Filter) Filter} must be specified before calling
 * {@link #onStartup(ServletContext)}. Registrations can be associated with
 * {@link #setUrlPatterns URL patterns} and/or servlets (either by {@link #setServletNames
 * name} or via a {@link #setServletRegistrationBeans ServletRegistrationBean}s. When no
 * URL pattern or servlets are specified the filter will be associated to '/*'. The filter
 * name will be deduced if not specified.
 *
 * @param  the type of {@link Filter} to register
 * @author Phillip Webb
 * @since 1.4.0
 * @see ServletContextInitializer
 * @see ServletContext#addFilter(String, Filter)
 * @see DelegatingFilterProxyRegistrationBean
 */
public class FilterRegistrationBeanextends Filter>
        extends AbstractFilterRegistrationBean {

    /**
     * Filters that wrap the servlet request should be ordered less than or equal to this.
     */
    public static final int REQUEST_WRAPPER_FILTER_MAX_ORDER = AbstractFilterRegistrationBean.REQUEST_WRAPPER_FILTER_MAX_ORDER;

    private T filter;

    /**
     * Create a new {@link FilterRegistrationBean} instance.
     */
    public FilterRegistrationBean() {
    }

    /**
     * Create a new {@link FilterRegistrationBean} instance to be registered with the
     * specified {@link ServletRegistrationBean}s.
     * @param filter the filter to register
     * @param servletRegistrationBeans associate {@link ServletRegistrationBean}s
     */
    public FilterRegistrationBean(T filter,
            ServletRegistrationBean... servletRegistrationBeans) {
        super(servletRegistrationBeans);
        Assert.notNull(filter, "Filter must not be null");
        this.filter = filter;
    }

    @Override
    public T getFilter() {
        return this.filter;
    }

    /**
     * Set the filter to be registered.
     * @param filter the filter
     */
    public void setFilter(T filter) {
        Assert.notNull(filter, "Filter must not be null");
        this.filter = filter;
    }

}

View Code

　　　　　　FilterRegistrationBean的类描述：一个用于向Servlet 3.0+容器注册Filter的ServletContextInitializer，类似于ServletContext提供的ServletContext＃addFilter（String，Filter）注册功能，但具有Spring Bean特性的友好设计。相当于对ServletContext＃addFilter进行了spring bean的友好性适配，本质还是ServletContext＃addFilter。

　　　　FilterRegistrationBean的类继承图

　　　　我们来看看ServletContextInitializer，感觉和ServeltContext有很大的关系，源码如下

/*
 * Copyright 2012-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.boot.web.servlet;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;

import org.springframework.web.SpringServletContainerInitializer;
import org.springframework.web.WebApplicationInitializer;

/**
 * Interface used to configure a Servlet 3.0+ {@link ServletContext context}
 * programmatically. Unlike {@link WebApplicationInitializer}, classes that implement this
 * interface (and do not implement {@link WebApplicationInitializer}) will not be
 * detected by {@link SpringServletContainerInitializer} and hence will not be
 * automatically bootstrapped by the Servlet container.
 * 

 * This interface is primarily designed to allow {@link ServletContextInitializer}s to be
 * managed by Spring and not the Servlet container.
 * 

 * For configuration examples see {@link WebApplicationInitializer}.
 *
 * @author Phillip Webb
 * @since 1.4.0
 * @see WebApplicationInitializer
 */
@FunctionalInterface
public interface ServletContextInitializer {

    /**
     * Configure the given {@link ServletContext} with any servlets, filters, listeners
     * context-params and attributes necessary for initialization.
     * @param servletContext the {@code ServletContext} to initialize
     * @throws ServletException if any call against the given {@code ServletContext}
     * throws a {@code ServletException}
     */
    void onStartup(ServletContext servletContext) throws ServletException;

}

View Code

　　　　ServletContextInitializer允许我们以编程方式配置Servlet 3.0+ ServletContext上下文，并且SpringServletContainerInitializer不会检测到实现此接口的类（类没有实现WebApplicationInitializer），因此不会被Servlet容器自动引导；ServletContextInitializer的设计目的是由spring管理，而不是Servlet容器。ServletContextInitializer就一个方法：onStartup，我们顺着FilterRegistrationBean的类图来看看onStartup的实现

　　　　我们发现，最终还是调用ServletContext的addFilter方法将Filter注册到Servlet容器。问题又来了，ServletContextInitializer的onStartup又是在哪里被调用的呢？

　　　　springboot的启动过程中肯定在哪个地方对ServletContextInitializer的onStartup进行了调用，我们接着往下看，我们从ServletWebServerApplicationContext.java的createWebServer方法开始（Springboot启动开始到createWebServer的过程就省了）

　　　　先去spring的beanFactory中获取ServletContextInitializer的全部实例，并将其放入到ServletContextInitializerBeans的initializers中，然后遍历initializers，调用每个ServletContextInitializer的onStartup方法（有人感觉这里有点多余，其实你把initializers想成缓存就好理解了，肯定还有其他地方会用到initializers）。

　　　　至此也就通了，spring将@Bean修饰的RegistrationBean注册到beanFactory，然后从beanFactory中获取全部的ServletContextInitializer，遍历它们并调用他们的onStartup方法将RegistrationBean中的bean注册到servlet容器；但是有一点@Bean注解是如何将bean注册到beanFactory的本文没有涉及，会放到springboot启动系列篇中，敬请期待。

总结

　　1、ServletContext是request与response交互的平台，也是我们的web应用与servlet容器沟通的桥梁；就从本文来说，Filter、Servlet、Listener的注册都是通过ServletContext来实现的

　　2、Servlet3.0+有很多新特性，包括Filter、Servlet、Listener的注册，不再只是通过web.xml实现了。而springboot也只是对ServletContext的add系列方法进行了拓展，使得具有spring的友好性，而FilterRegistrationBean就是具体的实现之一。

　　3、springboot启动过程中，调用ServletContextInitializer类型的实例的onStartup方法，完成指定bean到servlet容器的注册；指定bean就是指我们自定义的Filter、Servlet、Listener，而不是RegistrationBean类型的实例。

参考

　　《深入分析Java Web技术内幕》